class_docstr: `OperatorPool` manages `Operator` creation, acquisition, release, and garbage
  collection. Each `TaskExecutor` has one `OperatorPool`.
class_docstr_tok: ["`","OperatorPool","`","manages","`","Operator","`","creation",",","acquisition",",","release",",","and","garbage","collection",".","Each","`","TaskExecutor","`","has","one","`","OperatorPool","`","."]
code: def __len__(self):
      num = 0
      for _, op_storage in self._all_ops.items():
          num += len(op_storage)
      return num
  
file_path: towhee/towhee/runtime/operator_manager/operator_pool.py
imports: from typing import Dict, List
  import threading
  from towhee.operator import Operator, SharedType
  from .operator_loader import OperatorLoader
label_desc: Use image node_id 2 for calling the OperatorPool obj's underlying member method code with example usage: obj.__len__() and returns: num